Propulsion systems having an internal combustion engine powered by fossil fuel generate exhaust gas that comprises various components. The components of the exhaust gas generally include substances such as nitrogen, water vapor, carbon dioxide, hydrocarbons, nitrogen oxides, and particulate matter. Hydrocarbons result from the incomplete combustion of the fuel. Nitrogen oxides result from excessive combustion temperatures.
To reduce emission of undesirable substances in the atmosphere, various technologies are known. For instance, with respect to reducing emission of nitrogen oxides in the atmosphere, it is known to use activated carbon filters on stationary diesel engines used for power generation in a closed environment, such as in a mine. The exhaust gas of the stationary diesel engine is passed through an activated carbon filter and some components of the exhaust gas get loaded therein due to the adsorption properties of the activated carbon. When the activated carbon filters are saturated with nitrogen oxides, they are removed from the stationary diesel engines and replaced, or “purged” at a separate location by heating the activated carbon filter to remove the nitrogen oxides that were loaded therein. The handling required for the replacement or purge of the activated carbon filters may lead to high operating costs.
Other known technologies to reduce emission of undesirable substances in the atmosphere, such as exposing the exhaust gas to a catalytic converter, may not be suited for all types of propulsion systems powered by fossil fuel. For instance, as catalytic converters are most efficient at temperatures above 425° C., they may not be efficient for propulsion systems powered by fossil fuel having exhaust gas temperatures below 425° C. It is known to channel exhaust gas to an activated carbon filter after engine start and until the engine and exhaust reach a high enough temperature, after which the exhaust gas is channelled to a catalytic converter. In addition, the use of a catalytic converter may lead to an increase in costs of the propulsion system.
Therefore, there is a desire for a propulsion system that would reduce emission of undesirable components of the exhaust gas in the atmosphere while reducing the costs of the propulsion system and/or of its operation.